Aluminum retention maze and getter

ABSTRACT

Aluminum or aluminum foil is placed in communication with the interior of a cold cathode gas discharge display chamber to prevent undesirable quantities of mercury from entering the display chamber and to absorb undesirable O2 and H2O which may evolve during the life of the display device.

Paine, Jr. et al.

[ ALUMINUM RETENTION MAZE AND GETTER [75] inventors: Rigaud B. Paine, .lr., Dallas;

Michael Peshock, Jr., Richardson, both of Tex.

[73] Assignee: Texas Instruments Incorporated,

Dallas, Tex.

[22] Filed: Apr. 10, 1974 [2]] Appl. No.: 459,819

[52] US. Cl 313/177; 313/174 [5|] Int. Cl. H011 61/26 [58] Field of Search 313/174, 177

[56] References Cited UNITED STATES PATENTS 3,828,218 8/1976 Fehnel 313/177 [451 May 27, 1915 Primary Examiner-R. V. Rolinec Assistant ExaminerDarwin R. Hostetter Attorney, Agent, or Firm-Harold Levine; Edward J. Connors, Jr.; Stephen S. Sadacca [57] ABSTRACT Aluminum or aluminum foil is placed in communication with the interior of a cold cathode gas discharge display chamber to prevent undesirable quantities of mercury from entering the display chamber and to absorb undesirable O, and H 0 which may evolve during the life of the display device.

10 Claims, 2 Drawing Figures PATErJIEBam 27 I975 FIG. 2

ALUMINUM RETENTION MAZE AND GE'I'IER BACKGROUND OF THE INVENTION This invention relates to a gas discharge display panel of the type employed in calculators wherein a display gas such as neon with a trace of mercury therein is controlled by utilization of a metallic body placed on the interior of the device to form with excess mercury a reaction product which absorbs and H 0 which may evolve during use of the panel.

Gas discharge display panels generally include a suitable ionizable gas such as neon, argon, and krypton, singly or in combination, with a vapor of a metal such as mercury. Mercury is employed to minimize cathode sputtering.

It has been found that during use of such display units, undesirable O and H 0 evolves and causes the system to deteriorate in its performance.

PRIOR ART Cold cathode gas discharge display panels typically include a glass cover plate spaced from but sealed to a ceramic base plate or substrate to enclose one or more intermediate layers which form a completed display panel. The enclosure is charged with a desired gas at relatively low pressure. A heat-sensitive glass capsule filled with mercury, when broken by heat, causes the mercury violently to be expelled from the capsule in the form of both vapor and droplets. The presence of mercury droplets on the cathode display segments adversely affects the operation of the system.

SUMMARY OF THE INVENTION In accordance with the present invention control of the mercury and absorption of oxygen and water products which may evolve from the glass and other components of the structure during the life of the display panel is achieved through use of an aluminum foil suitably housed in communication with the chamber formed in the display unit. More particularly, aluminum, preferably aluminum foil, is included in a channel communicating with the display chamber. The aluminum prevents mercury droplets from being introduced into the display chamber while permitting desirous mercury vapor to pass into the chamber. Further, during use the aluminum is employed as a getter to prevent the accumulation of oxygen or water products in the display chamber.

More particularly, in accordance with the present invention, a cold cathode gas discharge display panel having a suitable excitation gas therein is provided with means forming a flow channel leading into the panel, and with a body of aluminum in the flow channel to react with mercury therein to form a material absorbant to oxygen and water products which may evolve in the course of display panel use. In a more specific aspect, a display panel having a base substrate upon which cathode members are formed in provided with a passage leading therethrough and connected into a chamber on the side of the substrate opposite the cathode, with a body of aluminum exposing a large surface area sealed there within and thus communicating with the display chamber between the control electrodes of the display panel to form a getter for accumulations of oxygen or water in the display chamber.

DESCRIPTION OF THE DRAWINGS For a more complete understanding of the present invention and for further objects and advantages thereof, reference may now be had to the following description taken in conjunction with the accompanying drawings in which:

FIG. I is a sectional side view of an illustrative embodiment of the invention including a gas discharge display panel with attached tubulation', and

FIG. 2 is a perspective view from the top of a display panel.

DESCRIPTION OF A PREFERRED EMBODIMENT FIGS. 1 and 2 illustrate a cold cathode gas discharge display panel. The display panel comprises a semiconductor substrate 16 upon which there are formed a plurality of metallic busses such as the bus I5. Over the substrate 16 and the busses 15 there is provided an in sulator 14 on top of which are formed a plurality of cathode electrodes 13. The cathode electrodes are selectively connected to the busses I5 by way of holes through the insulation called vias 22. A transparent cover plate 11 is spaced above but sealed to the substrate 16 at the edges thereof to form a chamber 26. Anode electrodes generally are of transparent thinfilm metallic layers 12. They are formed on the underside of the cover plate 11.

When a suitable gas is present, such as neon, krypton, argon, etc., within the chamber 26, the application of relatively low potential between the cathode l3 and anode 12 causes the gas to glow over an area corresponding generally to the surface area of the cathode 13. It has been found desirable in order to prevent sputtering to include relatively small amounts of mercury vapor in the chamber 26 along with the excited gas.

It has further been found that in the operation of such a system, continued use results in the accumulation of oxygen (0 and water (H O) in the chamber 26. This causes a deterioration of the operation of the system. Further, the presence of liquid mercury in chamber 26 causes degradation of the display quality.

In accordance with the present invention, the system of FIG. I is provided with a tube structure connected to the chamber 26 through a port 17. The tube structure includes a terminal fitting 19 connected by tube 25 to a bulb 20 which in turn is connected by way of a tube 24 to a source fitting 23. This structure is employed for charging the chamber 26 with the desired gas and with the mercury. Normally, chamber 26 is charged by heating the display unit while evacuating all of the gas therein through source fitting 23. After the chamber 26 is exhausted, the desired charge of display gas such as neon is introduced in a controlled manner through fitting 23. Prior thereto bulb 20 has been provided with a capsule 21 of mercury. The capsule 21 is of the type which deteriorates upon heating. After the display gas is introduced into the chamber 26, the bulb 20 is heated, thereby causing the capsule 21 to be broken. When broken, mercury erupts through tube 25, fitting 19, and port 17 so that mercury vapor in small amounts is injected into chamber 26. Heretofore, it has been found that mercury droplets also are propelled through port 17 and sometimes lodge on the surface of the elec trodes 13. Such mercury in liquid form in the chamber 26 degrades the quality of the display and is thus undesirable.

In accordance with the present invention, a body 18 of aluminum, such as crinkled aluminum foil or other type of aluminum which provides exposure of a large surface area for a given volume, is housed within the fitting 19. When chamber 26 is charged, body 18 serves to arrest the travel ofliquid mercury droplets, preventing them from passing through the port 17 into chamber 26. After the charging of the display unit has been completed, the fitting 19 is sealed by closing the tube 25 and removing bulb 20 and the remainder of the elements. Thus, the fitting 19 remains a permanent part of the display unit with the aluminum always present and in communication with the chamber 26 by way of the port 17.

Liquid mercury contacting body 18 forms a material absorbant to oxygen and water. More particularly, the absorption of oxygen and water by the body 18 may be understood from the following relationship:

Al(Hg) H O Al O .H O.

Thus a mercury and aluminum amalgum is formed by the presence of the aluminum foil in liquid mercury. The amalgum in turn will combine with the oxygen and water vapor evolved during the life of the display device to form a tree-like crystal formation or dendrite, composed of hydrated aluminum oxide. Thus, the pres ence of the aluminum not only inhibits the flow of mercury droplets into the display chamber, but also absorbs the harmful oxygen and water vapor which may be evolved during the life cycle of the display device.

Thus, aluminum or aluminum foil is placed in fitting 19 attached to the base substrate 16 of a gas discharge display panel. Fitting 19 also is connected by tube 25 to bulb 20 enclosing a glass capsule 21 filled with mercury. The aluminum is placed between the glass capsule 21 and the substrate 16 to prevent the admission of mercury droplets into the display chamber, Further, the absorbant characteristics of the aluminum-mercury reaction product prevents the accumulation of oxygen and water vapor in the display chamber.

In one embodiment of the invention, the port 17 is of 0.060 inches in diameter and is spaced from any boundary of cathodes such as cathode 13. Body 18 has a surface area of 2 square inches and is formed by aluminum foil of 0.002 inches, Body 18 is positioned in the path leading to port 17, not to close it off or prevent vapor or gas flow but to prevent travel of liquid droplets when capsule 21 is broken,

Having described the invention in connection with certain specific embodiments thereof, it is to be understood that further modifications may now suggest themselves to those skilled in the art and it is intended to cover such modifications as fall within the scope of the appended claims.

What is claimed is:

l. in a gas discharge display panel where a display gas with mercury atmosphere is retained in a chamber between display control electrodes, the combination which comprises an aluminum body in surface communication with the atmosphere in said chamber for interacting with said mercury and forming a product to serve as a getter for O and H which evolve during energization of said display.

2. In a gas discharge display panel wherein a display gas with mercury atmosphere is retained in a chamber between display control electrodes, the combination which comprises an aluminum body convoluted to pro vide exposure ofa relatively large surface area per unit volume in surface communication with said atmosphere in said chamber for interacting with said mercury and forming a product to serve as a getter for O and H 0 which evolve during operation of said display.

3. ln a gas discharge display panel where a display gas with mercury therein is retained in a chamber between display control electrodes some of which nest on a base substrate, the combination which comprises:

a, external tube means on the side of said substrate opposite said electrodes and flow communicating through said substrate to said chamber; and

aluminum-mercury amalgum in said tube means to serve as a getter for oxygen and water which evolves during use of said panel.

4. The combination set forth in claim 3 wherein said aluminum is in the form of crinkled foil.

5. Means for retaining excess mercury and absorbing undesirable quantities of oxygen and water vapor in a gas discharge display panel formed on a semiconductor base, which comprises:

a. external tube means attached to said base;

b. a heat-sensitive glass capsule filled with liquid mercury and sealed within said tube means; and

c. aluminum enclosed within said tube means at a location between said capsule and said substrate.

6. An apparatus for charging a gas discharge display panel to avoid liquid mercury in a display chamber and to absorb undesirable quantities of oxygen and water vapor, which comprises:

a. a base substrate for said panel having a port therethrough;

b. external tube means attached to said base substrate and communicating with said chamber through said port;

c. a heat-sensitive capsule filled with liquid mercury and positioned within said tube means; and

d. an aluminum body enclosed within said tube means between said capsule and said substrate, whereby upon evacuation of said chamber followed by charging with a display gas, heating of said capsule releases said mercury to introduce mercury vapor to said chamber and contact liquid mercury with said aluminum body to form materials absorbant to oxygen and water.

7. A method of control of mercury as to absorb undesirable oxygen and water products which may evolve during use of a gas discharge display panel to be charged with display gas and mercury vapor through external tube means leading to a chamber in said panel, which comprises:

a. placing a mercury-filled heatsensitive glass capsule in said tube means;

b. heating said capsule to free said mercury for passage of mercury vapor into said chamber; and

c. contacting excess liquid mercury from said capsule with aluminum within said tube means leading to said chamber to form material absorbant to oxygen and water 8. The method of claim 7 wherein said tube means is sealed to establish permanent flow communication between said chamber and said material.

9. A method of control of excess mercury and undesirable oxygen and water products which may evolve during the life of a gas discharge display panel charged with a display gas, which comprises:

gas with mercury therein is retained in a chamber between display control electrodes the combination which comprises an aluminum body in the form of crinkled foil placed in surface communication with said gas to react with said mercury and serve as a getter of O and H 0 which evolve during use of said display, said body being housed in a receptacle formed outside said chamber in flow communication with said chamber.

* k a: t 

1. IN A GAS DISCHARGE DISPLAY PANEL WHERE A DISPLAY GAS WITH MERCURY ATMOSPHERE IS RETAINED IN A CHAMBER BETWEEN DISPLAY CONTROL ELECTRODES, THE COMBINATION WHICH COMPRISES AN ALUMINUM BODY IN SURFACE COMMUNICATION WITH THE ATMOSPHERE IN SAID CHAMBER FOR INTERACTING WITH SAID MERCURY AND FORMING A PRODUCT TO SERVE AS A GETTER FOR O2 AND H2O WHICH EVOLVE DURING ENERGIZATION OF SAID DISPLAY.
 2. In a gas discharge display panel wherein a display gas with mercury atmosphere is retained in a chamber between display control electrodes, the combination which comprises an aluminum body convoluted to provide exposure of a relatively large surface area per unit volume in surface communication with said atmosphere in said chamber for interacting with said mercury and forming a product to serve as a getter for O2 and H2O which evolve during operation of said display.
 3. In a gas discharge display panel where a display gas with mercury therein is retained in a chamber between display control electrodes some of which nest on a base substrate, the combination which comprises: a. external tube means on the side of said substrate opposite said electrodes and flow communicating through said substrate to said chamber; and aluminum-mercury amalgum in said tube means to serve as a getter for oxygen and water which evolves during use of said panel.
 4. The combination set forth in claim 3 wherein said aluminum is in the form of crinkled foil.
 5. Means for retaining excess mercury and absorbing undesirable quantities of oxygen and water vapor in a gas discharge display panel formed on a semiconductor base, which comprises: a. external tube means attached to said base; b. a heat-sensitive glass capsule filled with liquid mercury and sealed within said tube means; and c. aluminum enclosed within said tube means at a location between said capsule and said substrate.
 6. An apparatus for charging a gas discharge display panel to Avoid liquid mercury in a display chamber and to absorb undesirable quantities of oxygen and water vapor, which comprises: a. a base substrate for said panel having a port therethrough; b. external tube means attached to said base substrate and communicating with said chamber through said port; c. a heat-sensitive capsule filled with liquid mercury and positioned within said tube means; and d. an aluminum body enclosed within said tube means between said capsule and said substrate, whereby upon evacuation of said chamber followed by charging with a display gas, heating of said capsule releases said mercury to introduce mercury vapor to said chamber and contact liquid mercury with said aluminum body to form materials absorbant to oxygen and water.
 7. A method of control of mercury as to absorb undesirable oxygen and water products which may evolve during use of a gas discharge display panel to be charged with display gas and mercury vapor through external tube means leading to a chamber in said panel, which comprises: a. placing a mercury-filled heat-sensitive glass capsule in said tube means; b. heating said capsule to free said mercury for passage of mercury vapor into said chamber; and c. contacting excess liquid mercury from said capsule with aluminum within said tube means leading to said chamber to form material absorbant to oxygen and water.
 8. The method of claim 7 wherein said tube means is sealed to establish permanent flow communication between said chamber and said material.
 9. A method of control of excess mercury and undesirable oxygen and water products which may evolve during the life of a gas discharge display panel charged with a display gas, which comprises: a. placing a mercury-filled, heat-sensitive glass capsule in a charging path leading to said panel; b. enclosing aluminum within said path between said capsule and said panel; and c. heating said capsule to release said mercury for flow of mercury vapor into said panel and for contact between said aluminum and liquid mercury to form a material which is absorbant to oxygen and water.
 10. In a gas discharge display panel where a display gas with mercury therein is retained in a chamber between display control electrodes the combination which comprises an aluminum body in the form of crinkled foil placed in surface communication with said gas to react with said mercury and serve as a getter of O2 and H2O which evolve during use of said display, said body being housed in a receptacle formed outside said chamber in flow communication with said chamber. 